1. Field of the Invention
The present invention relates to an optical waveguide substrate with an optical fiber fixation groove, a process for its production, stamps for use in this production process, and an opto-electronic hybrid integrated module including the optical waveguide substrate.
2. Description of the Related Art
Along with the practical applications of optical transmission systems, techniques relevant to optical waveguides as their basic components have drawn much attention. An optical waveguide has, typically, an embedded type structure in which a core layer having a high refractive index is surrounded with a cladding layer having a low refractive index, or a ridge type structure in which a core layer having a high refractive index is formed on a lower cladding layer having a low refractive index and an upper cladding layer is an air layer. Thus, light incoming to the optical waveguide is transmitted in the core layer while being reflected at the interface between the core layer and the cladding layers or at the interface between the core layer and the air layer.
In general, at the connection portion or terminal portion of an optical fiber to be used for optical transmission systems, an optical waveguide is used to connect the optical fiber with another optical fiber or to communicate optical signals with a light receiving element and a light emitting element. As a method for optical coupling of an optical fiber with an optical waveguide, an optical fiber fixation groove is formed, in series with a core layer of the optical waveguide, on a base substrate on which the optical waveguide is formed, and the optical fiber is inserted into and fixed in the fixation groove, for the purpose of carrying out optical axis adjustment in a simple and easy manner.
For example, Japanese Patent Laid-open Publication (Kokai) No. Hei 8-313756 discloses a method of forming an optical fiber fixation groove on a silicon substrate by reactive ion etching and then forming an optical waveguide made of glass fine particle films in the vicinity of the optical fiber fixation groove. Further, Japanese Patent Laid-open Publications (Kokai) Nos. 2000-105324 and 2000-131556 disclose methods of forming an optical waveguide made of a siloxane polymer on an alumina ceramic substrate and then forming an optical fiber fixation groove by dicing. Further, Japanese Patent Laid-open Publication (Kokai) No. 2004-198653 discloses a method of forming a quartz-type optical waveguide on a silicon substrate and then forming an optical fiber fixation groove by anisotropic etching (e.g., wet etching).
However, if an optical waveguide and an optical fiber fixation groove are formed separately on a base substrate, it is needed to carry out precise positioning between the core of an optical fiber and the core layer of the optical waveguide, and therefore, it results in a problem that the production process becomes complicated. Therefore, Japanese Patent Laid-open Publication (Kokai) No. 2004-347895 discloses a method of producing a base substrate having an optical fiber fixation groove and a core groove by press forming the base substrate with a master die having a convex portion corresponding to the optical fiber fixation groove and a convex portion corresponding to the core groove for forming the core layer of an optical waveguide. According to this method, once a master die is produced, every time of forming an optical waveguide and an optical fiber fixation groove, it becomes no need to carry out precise positioning between the core of an optical fiber and the core layer of an optical waveguide, and therefore, it results in an advantageous effect that production efficiency can be improved.